The market for cellulose products is buoyant, with increasing demand for fibres in Asia. The textile market contains both conventional clothing (apparel) textiles as well as the more and more important technical textiles, which are used principally for their performance or functional characteristics rather than for their aesthetics, or are used for non-consumer (i.e. industrial) applications. Clothing textile market is predominantly (80%) based on cotton or polyester raw material use, both having questionable effects on environment.
Production of cotton requires a lot of water, artificial fertilizers and pesticides. Despite the un-sustainability of cotton, the product properties are appreciated by consumers as they have a good feeling to the touch (“close-to-skin-feel-good”).
The consumption of technical textiles is growing four times faster than for clothing, in terms of both value and volume. The market value for technical textiles reached a global turnover of 100 billion  in 2011 and is increasing rapidly, especially in Asia. Out of this only 6% is viscose, or other wood-based cellulosics. Between 1995 and 2005, the world's consumption of technical textiles has grown by 41%. Roughly one fourth of the raw material used in technical textiles is natural based fibres (cotton, wood pulp), representing 3.8 million tons in the year 2005. The global market for non-wovens was 7.05 million tons corresponding to a market value of about 19.8 billion euros in 2010, with an estimated increase to 10 million tons by 2016. The average growth (2010-2015) for all nonwovens and sustainable nonwovens is 8.5% and 12.7%, respectively, but in certain sectors the growth can exceed 25% p.a. The growth is expected to be further accelerated by the enhanced properties of sustainable materials. The main market segments in terms of volume for nonwovens are hygiene (31.8%), construction (18.5%), wipes (15.4%) and filtration (4.0%).
Currently, approximately three quarters of the global production of man-made cellulosic fibres are based on the Viscose process. (1) From an environmental point of view, however, it is questionable whether the Viscose technique should be further promoted. The utilization of large amounts of CS2 and caustic results in hazardous by-products, such as sulphur oxides, sulfides and other gases, with reduced sulphur, which may cause severe stress for the environment. Further, a substantial amount of sodium sulphate, generated through the neutralization of sulphuric acid, by sodium hydroxide, is present in the waste water.
Alternatively, the so-called Lyocell process can convert pulps, by direct dissolution in N-methylmorpholine-N-oxide (NMMO) monohydrate, into value-added products. The first patents on the manufacture of Lyocell fibres were filed by American Enka/Akzona Inc (U.S. Pat. No. 4,246,221), later by Courtaulds and Lenzing AG (EP 0 490 870, EP 0 490 870). The wood-pulp is dissolved in a solution of hot NMMO monohydrate and in contrast to the Viscose process, the spinning dope is not extruded directly into the coagulation medium (wet spinning) but passes an air gap and remains as a liquid filament for a short period of time. By drawing the fibre, before and in the coagulation zone, the characteristic high tensile strength of Lyocell fibres are gained, which—unlike Viscose fibres—remains high even under wet conditions (2).
However, the versatility of the Lyocell process is limited by certain intrinsic properties of NMMO resulting from its peculiar structure. The N—O moiety impedes the implementation of redox-active agents whereas the cyclic ether structure is prone to so called thermal runaway reactions (potentially also due to the N-oxide functionality) necessitating appropriate stabilizers (3, 4).
Ionic liquids could offer a possibility to bypass these problems (5).
WO 03/029329 A2 claims the dissolution and possibility of regeneration of cellulose in a variety of ionic liquids. DE 102005017715 A1 and WO 2006/108861 A2, and WO 2011/161326 A2 describe the dissolution of cellulose in various ionic liquids and mixtures of them with amine bases, respectively. In WO 2007/101812 A1 the intentional homogeneous degradation of cellulose in ionic liquids is demonstrated. Details concerning the fibre spinning from ionic liquid solutions can be found in DE 102004031025 B3, WO 2007/128268 A2, and WO 2009/118262 A1.
The solvents described in the cited patent documents are mainly imidazolium-based halides and carboxylates. Halides are characterized by a pronounced corrosiveness towards metal processing equipment, whereas carboxylates, and in particular 1-ethyl-3-methylimidazolium acetate, show inferior viscoelastic properties for fibre spinning.